Valentino are testing

The Northern Territory Health Department is urging people to stay out of the water at five popular Darwin beaches this long weekend.

Casuarina is the latest beach to be closed after tests confirmed unsafe levels of E.coli in the water.

The department has not ruled out human waste as the cause, but says algae is more likely to be behind the problem.

The department's director of environmental health, Xavier Schobben, says further tests will be Valentino conducted in deeper waters.

"What we are doing is taking controlled samples from other sites in deeper water to give us a better idea of the overall extent of E.coli in the harbour," he said.

"We are tending to think this is more environmental-related and less related to any faecal contamination."

Meanwhile, the Environment Minister, Karl Hampton, has hit back at criticism over a lack of monitoring of water quality in Darwin harbour.

He says there are testing sites in and around the harbour and the Environment Department's monitoring regime is significant.

"I can reassure people that through my agency, we've got 51 monitoring sites throughout the Darwin Harbour and some of the estuaries around that are coming in," he said.

"We have strong Valentino Shoes Sale conditions under the Water Act, conditions that licensees who have discharge water licenses need to meet, and I think there's appropriate measures in place to protect the harbour."